1. Field of the Invention
The present invention relates to a raised access floor construction. In particular, it relates to a precast prestress raised access floor modular construction utilizing precast concrete components, pedestal support members and raised access floor panels.
2. Description of the Related Art
Access floors are of a double floored construction and are commonly used to create a free space between a sub-floor and the normal working environment of a room. Raised access floor systems are so constructed that floor panels are mounted on a surface of a poured in place topping layer overlying a precast concrete system. The topping layer is necessary to level camber deflection in the precast prestress concrete base floor. The floor panels are mounted on the surface of the overlying topping layer, by means of support pedestal legs attached to base plates often glued to the topping layer, whereby an under floor air delivery system may be provided between the floor panels and the topping layer. The pedestal support legs are stationary and are typically attached to the surface of the topping layer at predetermined positions. A corner portion of each of the floor panels is disposed at the upper end of the stationary pedestal support leg. Such systems are so constructed so as to provide an easy distribution of cabling and ventilation, and such systems are well known in the art.
For example, U.S. Pat. No. 5,048,242 to Cline discloses an access floor system having a plurality of floor panels each having a pan and a cooperating top plate. The top plate is folded over a peripheral flange of the pan to define a hemmed edge. The support pedestal assembly includes a support plate configured to support the floor panels at their corners. T-shaped stringers are joined to the support plates in a grid-like pattern. The stringers are rigidly connected to the plates or snap-on to lock tabs defined by the plates. In this manner, the pedestals support the panels, at their corners, with additional support provided along the edges of the panels using the stringers. According to this construction, each pedestal support member is secured to a surface of a topping layer poured in place over the base floor or to a construction framed of wood.
In yet another example, U.S. Pat. No. 5,072,557 to Nake et. al., discloses a device for fixing floor panels mounted on a surface of a base floor by means of using support legs which permit vertical adjustment of the floor panels. The fixing device includes a retainer plate, fixed to the base floor, for receiving the support legs, a support member extending vertically from the retainer plate and having an internally threaded portion, a panel holder, and a bearing member for the panel holder. The bearing member includes one end thereof threaded into the internally threaded portion of the support member for rotatable movement of the bearing member relative to the retainer plate. The bearing member is adapted to be accessible through the floor panels for operation. The panel holder is adapted to be engageable with the bearing member in order fix the floor panels.
While the foregoing systems disclose a plurality of floor panels of a type supported at a corner portion of each of the floor panels by a stationary pedestal support leg, a problem exists in the prior art when constructing an access floor on precast prestress concrete slabs because the slabs necessarily include a camber deflection which, requires the poured in place topping layer, or diaphragm, overlying the precast concrete slab in order to create a level surface for mounting the pedestal support legs. However, the poured in place overlying topping layer must be left in place for a sufficient time, often many days, to allow the topping layer to cure until it develops adequate strength. This eliminates the rapid erection advantage of precast prestress concrete construction over a poured in place construction and also increases building height. Therefore, what is needed is a precast prestress concrete construction for a raised access floor utilizing both precast prestress concrete floor slabs and raised access floor panels without the necessity of applying a poured in place overlying topping layer, framed construction, or diaphragm to overcome the camber deviation. The present invention satisfies these needs.